Refrigeration heat exchange process and apparatus



July 26, 1966 R. w. ALEXANDER 3,262,231

REFRIGERATION HEAT EXCHANGE PROCESS AND APPARATUS Original Filed Sept. 6, 1960 IN VENTOR. EOBEET m ALA'XAA/DEE IR BY y (izgfi PATENT AGENT Unitcd States Patent 3,262,281 REFRIGERATIQN HEAT EXCHANGE PROCESS AND APPARATUS Robert W. Alexander, 4041 Reedhurst, San Jose, Calif.,

assignor to Crystal-Aire Manufacturing Corporation,

San Jose, Calif, a corporation of California Continuation of application Ser. No. 53,988, Sept. 6, 1%0.

This application Jan. 9, 1964, Ser. No. 338,281 8 Claims. (Cl. 62-115) pertains have been utilized for refrigeration, air conditioning, and heating. They generally employ as a working substance a low boiling point or volatile liquid such as carbon dioxide, ammonia, or more commonly, one of the halogenated hydrocarbons commercially known as Freon, which volatile liquid is continuously cycled between a high pressure zone and a low pressure Zone. In moving from the high pressure zone to the low pressure zone, an expansion of the liquid into a vapor or gaseous state is achieved with a resultant reduction in temperature in accordance with the pressure, temperature, and volumetric relations of existent thermodynamic theory. Conventionally, the high pressure of the liquid is created by a compressor or equivalent mechanism and some form of flow restrictive element separates the high pressure zone from the low pressure zone. For such restriction, automatic or thermostatically controlled expansion valves are normally employed; in some instances, a capillary tube has been alternatively utilized. Regardless of its particular form, the restrictive element is arranged in accordance with presently existing refrigeration and air conditioning practice to provide .a large degree of restriction and consequently a large pressure differential between the high and low pressure zones. This accepted practice is predicated upon the general principle that the amount of useful heat transfer per unit flow of the volatile liquid increases in direct proportion to the pressure differential which, in turn, is directly proportional to the temperature differential.

Although the general principle is valid and commercial refrigerators, air conditioning systems, and heaters operating on such principle are indeed useful devices, very serious problems are encountered in their operation. This can be explained more readily by reference to a specific air conditioning system for a small residence of 1100 square feet of floor area. In accord with existing practice, adequate air conditioning would require a three ton system under normal environmental conditions, a unit ton in the air conditioning field representing a capacity of cooling at the rate of 12,000 B.t.u. (British thermal units) per hour. The high pressure in such a system will normally approximate 240 p.s.i. (pounds per square inch) and the low pressure perhaps 50 p.s.i. It will be immediately apparent that in order to achieve the stated pressure, a relatively large compressor must be employed. Conventionally, a three horsepower compressor unit is employed to match a three ton air conditioning evaporator unit, yet even with such power requiring high current the compressor unit is subjected frequently to overload conditions. As a result, not only is the efficiency of the entire air conditioning system rendered quite low, but considerable maintenance problems on the compressor unit itself are normally experienced. Furthermore, the compressor actually runs at an elevated temperature of approximately not only because of the heavy load thereon but additionally, because of the large amount of heat transferred to the Freon or other working substance in its passage through the evaporator coil of the system. The mentioned high pressure adversely effects operation of the compressor and also subjects the expansion valves to relatively large forces which ultimately result in further maintenance problems. Additionally, it is known that Freon will not mix with oil at such high pressure so that continuous lubrication of the system is not achieved and obviously with the higher pressure,- the possibility of leaks of the Freon or other working substance are increased proportionately. Partial loss of Freon in a conventional air conditioning system Will cause freezing of the coils which in the better air conditioning systems is avoided only through the addition of expensive automatic defrosting equipment. Thus are indicated some of the problems of heat exchange processes as presently employed.

Accordingly, it is a general object of the present invention to provide a heat exchange process and associated apparatus which shall be hereinafter generally re ferred to as a flooding system that is much more effective than existing systems for purposes of refrigeration, heating, air conditioning or other heat exchange applications.

More specifically, it is a feature of the invention to provide a heat exchange process wherein a relatively small pressure differential is utilized so that a substantial portion of the Freon or other working substance remains in the liquid state throughout the entire heat exchange cycle. I

It is another feature of the invention to provide a heat exchange apparatus which is not only more effective for its intended purpose but is less expensive to install and operate, and achieves considerable reduction in maintenance requirements.

A correlated feature relating particularly to the apparatus with which the process is carried out is the provision of a novel form of flow restricting element for creation of the required pressure differential in the system.

Yet another feature of the invention is the capability of the apparatus to embody a compressor unit of much lower rated capacity; a horsepower compressor unit can be utilized with a three ton evaporator coil for an air conditioning system.

A correlated feature is the reduction in the power requirement for a given installation and the avoidance of the compressor experiencing overload conditions. I

Another feature relating specifically to the compressor is the availability of the working substance at least in partially liquid form at the compressor input wherefore it can operate at normal room temperatures so as to be freed from many maintenance problems and have a greatly increased useful life.

A further advantageous feature of the invention relates to its capability of operation with a substantially re duced amount of Freon or other working substance when compared to conventional heat exchange arrangements of similar capacity.

A related feature of the invention is the freedom from the freezing problem existent in conventional systems when loss of the working substance occurs together with the reduced chance for such loss of the working substance because of the operation at considerably reduced pressure levels.

As a result of the reduced pressure in the system, another feature thereof is the capability of Freon to mix with the lubricating oil within the system so that all moving parts are continuously exposed to lubricant and thus are subjected to less destructive wear.

These as well as other objects and features of the invention will become more apparent from a perusal of the following description of the process and apparatus embodying the present invention.

Generally, the heat exchange process involves moving a volatile liquid such as Freon 22 through a closed cycle so that a continuous recirculation occurs. Initially, a relatively high pressure is created on the liquid and as the flow continues, the pressure is reduced an extent such that while some of the volatile liquid may undergo a change of state into its vapor form, at least a portion of the volatile liquid remains in the liquid state. With the described reduction in pressure, a corresponding reduction in temperature occurs in accordance with known thermodynamic principles and exposure of the cooled volatile liquid in appropriate relationship with a flow of air or other medium at a more elevated temperature will effect a heat exchange. After such heat exchange has occurred, the volatile liquid, or more particularly, the mixture of liquid and vapor is resubjected to the aforementioned higher pressure whereupon w-hatever vapor exists is returned through a condensation process to the liquid state. Upon subjecting the volatile liquid to the increased pressure, a corresponding increase in temperature is automatically effected and exposure of the heated volatile liquid in heat exchange relationship with cooler air or other medium completes the cycle of the entire heat exchange process.

If the process is to be applied, for example, to air conditioning, the low pressure heat exchange will take place within the residence or other zone to be cooled and the cooled and dehumidified air resulting from withdrawal of its initial heat int-o the working substance at the low pressure will be circulated as desired. In turn, the high pressure zone of the system will be located exterior of the residence and heat will be withdrawn from the high pressure, elevated temperature, volatile liquid through forced flow of environmental air in heat exchange relationship therewith. Preferably, in the air conditioning application, the pressure differential within the system is such that a substantial portion of the volatile liquid remains in its liquid state throughout the entire process, it being understood that a temperature in the low pressure zone of approximately 45 Fahrenheit is adequate. Accordingly, the amount of heat added to the volatile liquid 'within the residence is lIlSllfllClfillt to raise the temperature of the volatile liquid substantially and it is returned to the high pressure zone at a relatively low temperature. Since the relatively small pressure differential produces a correspondingly small temperature differential, the total cooling and dehumidifying effect per pound of working substance traversing the system is less, yet this same lowered pressure differential between the high pressure and low pressure zones of the system will enable a greater flow rate which more than compensates for the lessened pressure differential. Ultimately, more cooling and dehumidification can occur in a given period of time with considerably less expenditure of power. In short, efficieucy of the air conditioning operation is substantially increased.

Generally, substantially the same process can be employed for purposes of refrigeration, the major difference, of course, resulting from the necessity of producing temperatures in the neighborhood of Fahrenheit instead of 45 Fahrenheit required for the air conditioning system, as mentioned above. To produce such lower temperature, the pressure differential between the high pressure and the low pressure zones of the systemmust be increased ultimately resulting in a lower pressure in the low pressure zone such that the required temperature of approximately 0 Fahrenheit is obtained. With such increased pressure differential, a relatively greater portion of the volatile liquid will be transformed into the vapor state in the low pressure zone but in accordance with the present-invention, some of the volatile liquid always remains in the liquid state; wherefore a relatively low temperature is retained in the mixture of volatile liquid and vapor when it is returned to the high pressure zone of the system.

In order to utilize the described process for purposes of heating a residence, a simple reversal of the entire heat flow is merely required. More specifically, and with comparative reference to the description of the air conditioning system described hereinabo-ve, the high pressure zone of the system is now located within the residence while the low pressure zone of the system is located exteriorly thereof. Thus heat is added to the system from the exterior environmental air and is subsequentlywithdrawn from the system and into the circulating air within the residence. Depending upon the temperature difference between the air exterior of the residence and the desired temperature therewithin, the volatile liquid in its closed cycle circulation will remain either entirely in the liquid state in the high temperature zone or, as a mixture of liquid and vapor in the low temperature zone; but under all conditions, in accordance with the present invention, a portion of the volatile liquid remains in the liquid state throughout the entire heating cycle.

Additionally, it is to be expressly noted that in view of the alternative application of the present process to residence air conditioning and residence heating operation, heat exchange apparatus embodying the process can readily be arranged to serve both functions with suitable flow-switching arrangements, wherefore dual operation similar to that of the presently available heat-pump can be achieved.

Exemplary apparatus for carrying out the method and embodying additional aspects of the present invention is illustrated in the accompanying drawings wherein:

FIG. 1 is a diagrammatic representation of an apparatus for carrying out the above-described process for purposes of air conditioning, and

FIG. 2 is another diagrammatic representation of an apparatus for carrying out the process for purposes of industrial or residential heating.

With initial reference to FIG. 1, apparatus in the form of a three-ton air conditioning system such as utilized for conditioning the air in a residence of approximately 1100 square feet will be described by way of example. For clarification, it may be explained that a three-ton system, as herein referred to, means that a three-ton cooling coil indicated at 10 is utilized, such coil being capable of effecting a heat exchange at the rate of 36,000 B.t.u. (British thermal units) per hour. Such cooling coil 10 is located somewhere conveniently within the residence and Freon 22 or other volatile liquid discharged therefrom is delivered through a conduit 12 which for a threeton system is normally approximately /2 inch outside diameter to the suction side of a compressor unit 14 located exteriorly of the residence. Such compressor unit 14 can be of any commercially available type and will thus not be described in detail. However, it should be mentioned that rather than the three horsepower compressor unit utilized in conventional three-ton air conditioning systems, the compressor unit need only have a three-quarter horsepower rating for reasons to be explained in detail hereinafter.

The volatile liquid delivered through the conduit 12 to the compressor 14 at low pressure is discharged from the compressor at a substantially increased pressure through a conduit 16 into a heat exchange coil 18, also of conventional type. As a result of the increase in pressure by the compressor action, the volatile liquid is delivered into the coil 18 at a temperature in the neighborhood of Fahrenheit and heat is removed therefrom by a draft of air in heat exchange relationship with the coil under the energization of a suitable fan 24 After cooling of the volatile liquid, it is delivered through an additional conduit 22 into a liquid receiver or reservoir 24 and thence through a conduit 26 also of /2 inch outside diameter under high pressure toward the cooling coil 10.

Between the end of the conduit 26 and the entrance to the cooling coil 10, a flow restricting element 28 is positioned to provide the desired pressure. differential and the consequent reduction in temperature of the volatile liquid within the cooling coil 10. In accordance with the present invention, the flow restricting element for the described three-ton system constitutes a six foot length of tubing having an internal diameter of inch. It will be almost intuitively obvious that such a flow restricting element 28 does not provide a large degree of flow restriction; wherefore the pressure differential between the high pressure zone existing in the tubing 26 and the low pressure zone Within the cooling coil 10 is small as compared to conventional air conditioning systems. Actually, the pressure ditferential is such that the temperature within the coil for an air conditioning system is approximately 45 Fahrenheit and the volatile liquid, Freon 22, remains almost entirely in its liquid state.

For air conditioning purposes, a suitable blower is arranged to create a flow of air in heat exchange relationship with the coil 10 and partially in heat exchange relationship with the restrictive tubing 28 to provide for cooling of such air and dehumidification thereof at the same time. The cooled dehumidified air is delivered through a convetnional duct or ducts 32 to the various rooms of the residence, as desired.

In this heat exchange process, heat is obviously transferred into the volatile liquid within the coil 10 but the arrangement is such that the low pressure volatile liquid returned through. the conduit 12 of the section side of the compressor 14 is still at a relatively low temperature of, for example, 65 Fahrenheit, this being in contradistinction to the considerably higher temperature in the suction conduit of conventional air condition ing systems wherein the volatile liquid is vaporized entirely within an evaporator coil since a much greater amount of heat per pound of the volatile liquid flowing through such coil is absorbed. As a consequence, the compressor in the present system is actually cooled by the volatile liquid in the suction line 12 and can operate at a temperature at or below the environmental temperature. To the contrary, in conventional systems, compressors are found to operate at temperatures as high as 180 Fahrenheit which, obviously, increases wear and shortens compressor life.

Furthermore, the compressor is never subjected to a heavy load since the six foot length of inch tubing used as the flow restricting element in the described apparatus does not restrict flow to the extent achieved by operation of the expansion valves in conventional air conditioning systems. It is this reduction in the load requirements of the compressor which enables a horsepower compressor unit to be utilized in conjunction with a three-ton cooling coil.

Since the flow through the conduits is restricted but a comparatively small extent, such flow can be much more rapid so that even though the temperature differential between the high and low pressure zones of this apparatus are not as great as those existing in conventional air conditioning systems, the increased flow rate obtainable ultimately provides that a greater heat transfer to the air flowing through the coil 10 can be achieved in a given period of time for a given power input to the system. As a practical matter, for a given air conditioning installation, because of the noted increase in heat transfer, less power input is required.

Furthermore, because of the reduction in required size of the compressor unit, a considerable reduction in the total amount of the working substance utilized in the system can be effected. Such reduction in the amount of Freon 22 or other volatile liquid in the system together with the reduction in the pressures existing within the system precludes the adverse effects resultant from loss of Freon 22 as experienced frequently in conventional air conditioning systems. Additionally, because the Freon 22 is subjected to lower pressures during operation of this system, it can mix with the lubricants in the compressor and these are thus continually entrained and recirculated throughout the system with the Freon 22 so as to provide a constant source of lubrication for all moving parts. Consequently, not only is compressor life increased through its operation at lower temperatures, but through the constant automatic lubrication thereof.

If a seven-ton air conditioning system is desired, the coil 10 must have a rated capacity of seven tons, the compressor unit should be increased to approximately two horsepower, the conduits 12, 16, 22 and 26 should.

be increased to an internal diameter of approximately one and one-half inches and, in turn, the flow restricting element 28 will be increased in size to approximately inch internal diameter with substantially the same six foot length. These values are indicative of the general design requirements of any air conditioning system, but obviously, individual variations may be experienced between one installation and another. However, in any air conditioning installation, it is of paramount importance in accordance with the present invention to provide a reduction in the flow restriction to an extent such that a portion of the Freon 22 or other working substance remains in the liquid state throughout the entire cycle thus assuring maximum efiiciency of the heat exchange process and also longevity of the moving parts of the system, that is, the compressor unit, itself.

With reference to FIG. 2, apparatus utilizing the process for purposes of residential heating is illustrated. Es sentially, the same elements of the air conditioning apparatus illustrated in FIG. 1 and described hereinabove can be utilized in such heating system with the only essential change being in the positioning of the conduits and the flow restricting element so that basically a reversal ofthe air conditioning cycle is obtained. To indicate the similarity, elements of the heating system of FIG. 2 which correspond .to those of the air conditioning system of FIG. 1 will be indicated by like numerals but with an added prime notation.

The compressor 14' delivers high pressure Freon 22 or other volatile liquid through conduit 34 into a coil "10 which now functions as a heating coil. Sufiicient compression can be obtained with a three-quarter horsepower compressor unit to obtain a coil temperature of approximately 400 Fahrenheit. Over this coil 10', air from a blower 30 is passed and into the heating ducts 32' of the residence. The Freon 22 under high pressure is delivered from the heating coil 10' through the flow restricting tubing 28' and thence is returned under reduced pressure and consequently lowered temperature through conduit 36 to a coil 18' with an associated fan 20 which provides a draft of exterior air that adds heat to the cool volatile liquid within the coil. The heat added is insufficient to raise the temperature of the volatile liquid above 50 Fahrenheit and this relatively cool volatile liquid is returned through a suction conduit 38 to the compressor. Thus, in this heating cycle, as in the previously described air conditioning cycle, the compressor 14 is continually maintained at a relatively low temperature so as to increase its useful life.

Since the heating and air conditioning apparatus of FIGS. 1 and 2, respectively, utilize similar elements and merely essentially necessitate a reversal in the flow cycle, it is apparent that through the use of suitable valves, a single apparatus can serve either as an air conditioner or heating unit in a manner similar to the conventional heat-pump. Since the changes required for such conversion are substantially the same as those in the known heat-pump, they will not be described in detail.

For application to refrigeration processes, the basic action described hereinabove with respect to the air conditioning system can be employed, but with the additional change that, depending upon the refrigerating temperature desired, an increased pressure differential must be achieved and consequently, the internal diameter or length of the restrictive tubing must be varied. With such increased pressure differential, some of the volatile liquid can be transformed into the vapor state in the low pressure portion of the system, but in accordance with the principles of the present invention, some of the liquid must remain in the liquid state in order to achieve the advantages, as explained hereinabove.

Various other applications and specific modifications and/or additions can be made to the described process and the exemplary apparatus without departing from the spirit of the invention; and accordingly, the foregoing description of the process and apparatus is to be considered as purely exemplary and not in a limiting sense. The actual scope of the invention is to be indicated by reference to the appended claims.

What is claimed is:

1. A heat exchange process which comprises moving a volatile refrigerant liquid through a closed cycle, with a relatively high pressure on the liquid at one portion of the cycle, reducing the pressure in another portion of the cycle only to that extent where at least (five percent) by volume of the volatile liquid remains in the liquid state continuously during normal operation throughout the entire low side but a substantial temperature reduction is effected, thereafter increasing the pressure of the liquid and vapor and then reducing the temperature so as to condense that portion of the volatile liquid in the vapor state to reestablish the volatile liquid in a completely liquid state at the initial, relatively high pressure, and a correspondingly high temperature to thus complete the closed cycle.

2. A heat exchange process according to claim 1 which comprises adding heat to the moving volatile liquid when under reduced pressure by exposure in heat exchange relation to a relatively high temperature flowing fluid.

3. A heat exchange process according to claim 1 which comprises withdrawing heat from the moving volatile liquid when at a relatively high pressure by exposure in heat exchange relation to a relatively low temperature flowing fluid.

4. A heat exchange apparatus of the closed cycle type employing a volatile refrigerant liquid as a working substance which comprises means for moving the liquid, means for restricting the liquid flow whereby a pressure and conduit means connecting said liquid moving means,

restricting means, and said first and second heat transfer means to permit continuous recirculation of the volatile liquid through the closed cycle.

5. A heat exchangeapparatus according to claim 4 wherein said flow restricting means includes tubing having an internal diameter and a length such that the required pressure differential is established.

6. A heat exchange apparatus according to claim 5v wherein said liquid moving means constitutes a compressor.

7. A heat exchange apparatus according to claim 6 wherein said first heat transfer means adds heat to the working substance to an extent such that the volatile liquid enters said compressor at a temperature below the ambient environmental temperature. A

8. A heat exchange apparatus of the closed cycle type employing a volatile'refrigerant liquid as a working substance which comprises first heat transfer means through which the liquid can flow and arranged so that the pressure differential thereacross is insufficient to permit vaporization of all of the volatile liquid wherefore during normal operationat least 5% (five percent) by volume of the liquid refrigerant remains continuously in the liquid state at a reduced pressure, means connected to receive refrigerant from said first heat transfer means for moving the refrigerant and for increasing the pressure thereon and second heat transfer means connected between said refrigerant moving means and said first heat transfer means for removing heat from the refrigerant so as to return refrigerant in its liquid state to said first heat transfer means.

References Cited by the Examiner UNITED STATES PATENTS 2,532,452 12/ 1950 Hoesel 62511 2,807,940 10/1957 Urban 62511 2,969,655 1/1961 Salter 62-511 3,079,764 3/1963 Wescott 62467 MEYER PERLIN, Primary Examiner. 

1. A HEAT EXCHANGE PROCESS WHICH COMPRISES MOVING A VOLATILE REFRIGERANT LIQUID THROUGH A CLOSED CYCLE, WITH A RELATIVELY HIGH PRESSURE ON THE LIQUID AT ONE PORTION OF THE CYCLE, REDUCING THE PRESSURE IN ANOTHER PORTION OF THE CYCLE ONLY TO THAT EXTENT WHERE AT LEAST 5% (FIVE PERCENT) BY VOLUME OF THE VOLATILE LIQUID REMAINS IN THE LIQUID STATE CONTINUOUSLY DURING NORMAL OPERATION THROUGHOUT THE ENTIRE LOW SIDE BUT A SUBSTANTIAL TEMPERATURE REDUCTION IS EFFECTED, THEREAFTER INCREASING THE PRESSURE OF THE LIQUID AND VAPOR AND THEN REDUCING THE TEMPERTURE SO AS TO CONDENSE THAT PORTION OF THE VOLATILE LIQUID IN THE VAPOR STATE TO REESTABLISH THE VOLATILE LIQUID IN A COMPLETEL LIQUID STATE AT THE INITIAL, RELATIVELY HIGH PRESSURE, AND A CORRESPONDINGLY HIGH TEMPERATURE TO THUS COMPLETE THE CLOSED CYCLE. 